// let alphabet:NSString = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
//
//func randomAlphabet(length: Int) -> String {
//    let numberOfCharacters = alphabet.length
//    let digestLen = Int(CC_MD5_DIGEST_LENGTH)
//    let characters = UnsafeMutablePointer<unichar>.alloc(digestLen)
//    alphabet.getCharacters(characters, range: NSMakeRange(0, numberOfCharacters))
//
//    for i in 0..<numberOfCharacters {
//        let j = Int(arc4random_uniform(UInt32(numberOfCharacters - i))) + i
//        let c = characters[i]
//        characters[i] = characters[j]
//        characters[j] = c
//    }
//
//    let result = NSString(characters: characters, length: length)
//    free(characters)
//    return result as String
//}